about random number and matrix

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Zichao Wang
Zichao Wang 2020-5-25
评论： Walter Roberson 2020-5-26
If I have only one random number rand(1) , R1 (1X N) and R2(1XN) are both vector of size N.
R1=a*[0:n-1];
R2=b*[0:n-1];
R2=rand(1)+R2; % add rand(1) to every element in R2
del=R1-R2' ; % "row vector-column vector" is interpreted as "matrix-matrix" with appropriate duplication of rows and columns
But i want to do monte carlo simulation so I need a lot of rand(1). For example rand(1000000,1). But i dont want to use any loops since it is unefficient.
How can I still do the two steps above ?
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Walter Roberson
Walter Roberson 2020-5-25
That did not answer my question.
Your R1 is length n, and your R2 is length n as well, and you have 1000000 random numbers. What size of output of del do you want? n x n x 1000000 ? n x n x 1000000 x 1000000 ?
Zichao Wang
Zichao Wang 2020-5-25
I am not sure . I want each random can generate a corrponding del. So i need 100000 of del (n X n)
so n x n x 1000000 i guess

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Walter Roberson
Walter Roberson 2020-5-25
编辑：Walter Roberson 2020-5-25
R1=a*[0:n-1];
R2=b*[0:n-1];
R2=rand(1, 1, 100000)+R2.'; % add rand to every element in R2
del=R1-R2 ; % "row vector-column vector" is interpreted as "matrix-matrix" with appropriate duplication of rows and columns
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Walter Roberson
Walter Roberson 2020-5-26
Please re-check.
>> a = rand; b = rand; n = 5; R1=a*[0:n-1]; R2=b*[0:n-1]; R2=rand(1, 1, 100000)+R2.'; del=R1-R2 ;
>> size(del)
ans =
5 5 100000
Walter Roberson
Walter Roberson 2020-5-26
NB = 20; %number of bins
mind = min(del(:)); maxd = max(del(:));
bins = linspace(mind,maxd,NB); centers = mean([bins(1:end-1);bins(2:end)]);
counts = arrayfun(@(R,C) histcounts(del(R,C,:), bins), ndgrid(1:n,1:n), meshgrid(1:n,1:n), 'uniform', 0);
h = arrayfun(@(idx) bar(subplot(n,n,idx), centers, counts{idx}), 1:n^2);

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